Anthropogeny

Anthropogeny is the study of human origins, involving evolutionary, climatic, geographic, ecological, social, and cultural factors.

History
The main scientific evidence used to determine human origins includes fossil remains, radioactive dating methods, and genetic evidence (use of mitochondrial DNA and Y chromosome studies from indigenous peoples in relatively isolated parts of the Earth). Most of the fossils were found in Africa, where humanity originated. While the first human species, orrorin tugenensis, originated 6 million years ago, it was not until 3 million years ago that humans became bipedal. Homo habilis came to have a larger brain capacity, followed by another brain capacity improvement with homo erectus. Humanity left Africa 1.5 million years ago, and humans eventually involved into Homo neanderthalensis (which lived in Central Europe) and then into homo sapiens, the current human species.

Australopithicus afarensis, which lived 3 million years ago, was five-feet tall, and they were bipedal humans who originated in East Africa. Australopithices had chimpanzee-like teeth and bony eye ridges, but they had humanoid brain cases. Homo erectus was the first hominid species to migrate out of Africa, colonizing Asia and Europe; they originated 1.8 million years ago. In Europe, homo erectus gave rise to the humans known as Neanderthals. Homo erectus was taller than Homo habilis, had a larger brain, and had about the same level of sexual dimorphism as modern humans. Neanderthals lived throughout Europe from 200,000 to 40,000 years ago, and they had brains as large as homo sapiens, though somewhat different in shape. Neanderthals were generally more heavily built than modern humans. After homo sapiens came out of Africa 100,000 years ago, they travelled throughout the world and came into conflict with the Neanderthals. While members of the two species occasionally interbred, homo sapiens took over the Neanderthals' niches and massacred the surviving ones, emerging as the only surviving human race.

There are two alternative hypotheses that have been proposed for the origin of anatomically modern humans. In the multiregional hypothesis, fully modern humans evolved in parallel from the local populations of homo erectus. In this view, the great genetic similarity of all modern people is the product of occasional interbreeding between neighboring populations. The theory was once the predominant racial development theory in anthropology, but genetic studies have discredited this theory, which proposed independent evolution instead of the dispersion of humans and the eventual formation of races.

The other hypothesis, the Out of Africa or replacement hypothesis, argues that all Homo sapiens throughout the world evolved from a second major migration out of Africa that occurred about 100,000 years ago. This migration completely replaced all the regional populations of hominid derived from the first hominid migrations, and it was only 100,000 years ago that, following the dispersion, races such as African, European, Asian, and Australasian were formed due to acquired characteristics.

An allele is an alternate form of the gene. Most people have the normal gene (C) for making a normal C channeling protein; some people carry a mutated gene (c) that is defective. CC or Cc individuals are normal, while ccc individuals can have diseases such as cystic fibrosis. There are many different c alleles, and populations can be defined by the frequency of genes within it. Luigi Luca Cavalli-Sforza has been the most important geneticist who

Mitochondrial DNA has been used to establish human ancestry, as it is a small genome and easy to study. Mitochondrial DNA is inherited through the female, and mutations that are deleterious are most likely lethal. Mitochondrial DNA makes tracing ancestry much easier than using genes in the nucleus. There is an established "Molecular Clock" that has been established with the mutation rates of Mitochondrial Genes; the more genetic variations one sees in the mitochondrial genome the older the indigenous population group is.